A typical example of the conventional ornamental and protective molding as described above (hereinafter referred to simply as a "molding") is shown in the FIGURE, and is manufactured by a method generally referred to as potting, wherein a belt-shaped support 1 is first made of a synthetic resin with both lateral sides formed in an edge shape, and onto the top surface of the support 1a, a liquid transparent synthetic resin material with an appropriate viscosity is poured and cured to form a transparent synthetic resin layer 2 having a positive meniscus. This method is described in U.S. Pat. Nos. 4,446,179 and 4,566,929. According to this prior art reference, the transparent synthetic resin layer 2 is preferably made of a cured polyurethane that is the reaction product of a polyether polyol component (polypropylene glycol) and an aliphatic diisocyanate, for a molding having a desired resistance to both wear and shock; alternatively, the layer 2 is preferably made of a cured polyurethane that is the reaction product of (1) a mixture of a polyester glycol and a polypropylene triol of low to medium molecular weight and (2) an aliphatic diisocyanate/polypropylene triol adduct, for a desired flexible molding. In the FIGURE, the numeral 3 indicates a double-side adhesive tape, and 4 is a release paper.
The present inventors prepared samples of moldings wherein the transparent synthetic resin layer 2 was made of the two types of cured polyurethane and conducted various performance tests on these samples. As a result, the moldings were found to have the following defects.
(a) When the transparent synthetic resin layer was made of the cured polyurethane that was the reaction product of a polyether polyol component and an aliphatic diisocyanate component, the molding used as a side molding tended to generate cracking on the synthetic resin layer or peeling of the layer and the belt-shaped support because the molding was bent by a large curvature so that it would fit curved corners of the body of a vehicle.
(b) When the transparent synthetic resin layer was made of the cured polyurethane that was the reaction product of (1) a mixture of a polyester glycol and a polypropylene triol of low to medium molecular weight and (2) an aliphatic diisocyanate/polypropylene triol adduct, the above problems were partly resolved, but on the other hand, the resulting resin layer did not have a high degree of transparency since the polyol component was of a multi-component system having different molecular weights. Therefore, the second approach is not suitable for the case where a synthetic resin layer having a lens effect is desired.
In order to resolve these problems, the present inventors previously proposed that a tetraol which is an alkylene oxide adduct of ethylenediamine having a number average molecular weight of 1100 or less should be used as the polyol component of the cured polyurethane of which the transparent synthetic resin layer 2 is made.
When a molding in which the transparent synthetic resin layer 2 was made of a cured polyurethane using the above-specified tetraol as the polyol component was bent in a heated atmosphere (usually at about 70.degree. C.), the resin layer 2 could withstand bending by an appreciably large curvature (usually up to 1/20 cm.sup.-1) without occurring any cracking in the resin layer 2. However, with the recent trend toward more versatile design in the body of an automotive vehicle, the need for bending the molding by an even greater curvature (usually 1/15 cm.sup.-1) is increasing, and the resin layer 2 has been proved to be incapable of sufficiently withstanding bending under such severe conditions without generating any cracking.